文档介绍：Chapter 2 OSI Model & TCP/IP Protocol Suite
The OSI/RM
Layers in the OSI/RM
TCP/IP protocol suite
Addressing in TCP/IP
TCP/IP versions
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The OSI/RM
An ISO standard
Open System Interconnection/ Reference Model
开放系统互连/参考模型
Released in 1984
Ensured patibility and interoperability
7 layers, each of which illustrates a work function
ISO is anization, OSI is the model
OSI is not a protocol, but a conceptual model
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OSI Model
Application
Presentation
Session
Transport
Network
Data Link
Physical
7
6
5
4
3
2
1
应用层
表示层
会话层
传输层
网络层
数据链路层
物理层
网络支持层
(软/硬件)
应用支持层
(软件)
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Why Layered?
Advantages
plexity
Standardizes interfaces
Facilitates modular engineering
Ensures interoperable technology
Accelerates evolution
Simplifies teaching and learning
Disadvantages
Strict layered architecture makes its software not so efficient.
…
N+1
N
N-1
…
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The Features of Layering
Each layer concerns on its own details
Each layer provides a service to the layer above
Each municates with its peer layer in another node through the use of a corresponding protocol
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Peer-to-munication
对等进程/对等实体
(Peer Entity)
Peer Entity
对等进程/对等实体
对等层
Peer Layer
Peer Layer
对等层
Interface
接口
对等层协议
Peer-to-Peer Protocol
Peer-to-Peer Protocol
对等层协议
Service
服务
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Peer Layer vs. Peer Entity
Multiple entities in one layer
Peer entity:存在通信关系的对等层实体
Multiple protocols in one layer
Protocol:对等实体间的通信规则
CutFTP
FTP Server
Outlook
Mail Server
IE
Layer 7
Layer 7
Outlook
IE
CutFTP
FTP Server
Mail Server
FTP
HTTP
SMTP
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Data Exchange: Encapsulation
Source
Destination
A
P
S
T
N
DL
Ph
PDU:Protocol Data Unit
协议数据单元
帧 Frame
分组 Packet
数据段 Segment
数据 Data
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Postal Delivery
信件
邮局
分拣邮包
邮政网络
邮政运输
交通运输
信件
邮局
分拣邮包
邮政网络
邮政运输
信件格式
寄信方式
分拣邮包规则
邮路选择
运输方式
同层间需要约定规则——协议
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Layers in the OSI/RM
Application
Presentation
Session
Transport
Ne